1. Field of the Invention
The present invention relates to an optometric apparatus for a subjective examination of a visual function (a visual acuity, etc.) of an eye of an examinee.
2. Description of Related Art
There has been known an optometric apparatus for subjectively examining a visual function (e.g., a visual acuity, etc.) of an eye of an examinee by switchably disposing optical elements such as spherical lenses and cylindrical lenses in front of the examinee's eye and selectively presenting optotypes before the examinee's eye. Examinations using this type of optometric apparatus include a far vision examination for examining far vision and others by presenting the examination optotypes at a distance of 5 m from the examinee's eye and a near vision examination for examining additional power, near vision, and others by presenting the examination optotypes at a near distance of 15 cm to 70 cm from the examinee's eye.
In the near vision examination using the above conventional optometric apparatus, for example, an apparatus main unit 100 shown in FIG. 7, a rod 101 is attached to a support unit 111 hanging and supporting a right and left lens chamber units 110 which can be converged, and a chart 102 on which a number of examination optotypes for a near vision examination are drawn is placed at the tip end of the rod 101. An examinee (an examinee's eye) is asked to look at the chart 102 through the optical elements switchably disposed in test windows 110a of the lens chamber units 110. During the examination, the chart 102 is illuminated from above by the light of an illuminator 104, e.g., a fluorescent light or the like, mounted on a support arm 103 which supports the main unit 100.
However, the light of the illuminator 104 illuminating the chart 102 from above may cast the shadow of the rod 101 on the chart 102. Due to such shadow on the chart 102, the examination optotypes would become hard to see. Furthermore, if an inclination angle of the support unit 111 (the lens chamber units 110) with respect to the support arm 103 changes or the position of the chart 102 with respect to the support unit 111 (the lens chamber units 110) changes, it is necessary to adjust the orientation of the illuminator 104.
On the other hand, Japanese utility model unexamined publication No. Hei 6-46702 proposed an optometric apparatus in which an illuminator was mounted near a part at which a rod (bar) supporting a near vision examination chart is fixed, thereby making the illumination direction parallel with an axial or longitudinal direction of the rod. In this case, no shade of the rod is cast on the chart; however, the illuminator being placed near the fixing part of the rod, the chart placed on the same height as test windows of lens chamber units is also illuminated from a position higher than the chart. Consequently, when the chart is moved or slid frontward and backward in the axial direction of the rod to change a presenting distance (position) of the chart, the illumination light axis may not come to almost the center point of the chart. The brightness of the illumination light would therefore change depending on the presenting distance (position).